1. Field of the Invention
The present invention relates generally to pneumatic valves. More particularly, the invention concerns a multi-function, pneumatic valve for use in connection with spring applied air release parking brakes of the character used in heavy-duty truck trailers.
2. Discussion of the Invention
Parking brakes on most heavy-duty truck trailers are typically of the spring applied, air pressure release variety. For purposes of safety such brakes are maintained in a "brake on" configuration until air pressure, sufficient to overcome the locking force of the springs, is applied to the air chambers of the brake unit.
Single purpose, spring brake exhaust valves have for some time been commercially available. For example, such a valve is sold by Sealco Air Controls of Phoenix, Arizona under the model number 78021. Such valves are typically used in conjunction with one or more types of pressure protection valves. One such valve is also sold by Sealco Air Controls under the model number 140280. Another unit typically used in conjunction with the standard spring brake exhaust valve is a unit adapted to prevent compounding the application of the brakes. In the prior art, these three separate valves or units were separately installed into the truck-trailer pneumatic system.
The primary thrust of the present invention is to provide a novel valve assembly for use in conjunction with spring applied air release brakes which takes the features of three separate prior art devices and incorporates them into a single valve. In this way only one unit rather than three separate units need be installed in the truck-trailer pneumatic system. This not only simplifies installation, thereby substantially reducing installation costs, but also increases system reliability by significantly reducing the possibility of leaks.
As will be appreciated from the discussion which follows, the single valve of the present invention uniquely provides the required system pressure protection, prevents compounding application of the brakes and performs the brake release function in an efficient and highly reliable manner.